The present invention relates generally to the field of electrophotographic print machines, and in particular to a system and method of optimizing a motor drive system for changes in motor torque load such as that caused by single-color printing.
A variety of devices utilize electrophotographic print mechanisms to produce color image output, including printers, copiers, and multifunction machines that may include scan, copy, print, and fax operations in an integrated unit. Typically, the print mechanisms of such devices deposit and fuse four colors of toner—Cyan (C), Magenta (M), Yellow (Y), and Black (K)—onto a variety of media sheets to produce the color image output. Each color of toner is typically supplied in a removable cartridge, which includes a reservoir of toner, a photoconductive (PC) drum for selectively depositing the toner on a media sheet in response to a latent image produced by a laser, and various rollers and mechanisms for transferring the toner to, and depositing it on, the PC drum. The operation of electrophotographic print machines and toner cartridges are well known in the art. The toner transfer mechanisms and the PC drum of a toner cartridge are typically driven by a motor and associated drive train. Often, a motor may drive two or more toner cartridges. In one configuration, two motors may be utilized to drive four cartridges, i.e., one motor drives, e.g., the C and Y toner cartridges, and another motor drives the Y and K toner cartridges.
Color printing usually requires the use of at least the C, M, and Y toner colors, and often all four (CMYK). Black-only printing may be performed by use of only the K toner, or alternatively, by use of the C, M, and Y toner colors mixed together to produce black, a method known in the art as “process black.” In either case, the unused toner cartridge(s) may be removed. In this case, the motor driving the Y and K toner cartridges will experience only half of its nominal torque load (as it drives only one of two expected toner cartridges).
The motors in electrophotographic print mechanisms must be precisely controlled as to speed and position, to achieve high levels of accuracy in placing toner on media sheets, known in the art as dot resolution. To achieve this accuracy, sophisticated motor controller systems have been developed. In many cases, the parameters and variables of the motor control systems are carefully tailored, or “tuned,” to the actual anticipated motor operating conditions in a particular print mechanism implementation, including the expected motor torque load. When the torque load experienced by a motor is altered, such as by removal of one of the toner cartridges that the motor normally drives, it may alter the accuracy of speed and/or position control of the motor, thus degrading achievable dot resolution.